Present invention relates to an image processing apparatus and method thereof and, more particularly, to an image processing apparatus and method for expanding coded image data and performing a process appropriate for the characteristics of an image, as well as a computer-readable memory.
Various methods have been suggested lately for realizing effective image compression by mapping an image in a frequency region and performing appropriate quantization and encoding for each frequency component. Particularly popular method of image compression is image-matching-type image compression which is a combination of discrete cosine transformation (DCT) and Huffman coding, and which is adopted as an international standard. The xe2x80x9cimage-matching-type image compressionxe2x80x9d performs image processing suitable for an image type (e.g., natural image, CG, character-oriented/line-oriented image or the like). Along with recent penetration of color image systems, such technique for image compression is often utilized for compressing a color image with high quality (high resolution).
Among the general color image systems, particularly, the wide-use of a color printing system adopting an ink-jet color printer is known. Such color image system often applies color printing operation where a high-resolution color image is compressed and stored in a disk device (file system), and the compressed data is expanded as necessary, resulting in rapid improvement in the color printing system. Since memory capacity of the file system is limited, image compression processing is essential to color image system so long as increase in memory capacity leads to increase in cost.
However, the above described technique raises the following problems.
One of the factors which determines quality of an output image in a color image system, including a binary color output device such as the above described ink-jet color printer or the like, is the method of processing full-color image data into pseudo half-tone image data, that is, a binarization method.
For binarization methods, a dither method, an error diffusion method and the like are available, each of which is utilized depending upon the desired image quality or the processing speed. Generally, the error diffusion method is used for generating a high quality (high resolution) image but notorious for long processing time. The dither method is capable of high-speed processing, but known to provide a problem of conflicts in improvement of resolution and improvement of tonality because of the structure of the dither matrix. Although an image-matching-type dither processing for analyzing frequency components in a partial area of an image is provided to solve the foregoing problem raised by the dither method, the problem of long processing time still remains.
The present invention has been made in consideration of the above situation, and has as its object to solve the foregoing problems.
It is an object of the present invention to provide an image processing apparatus and method thereof which can obtain high-quality image data in a short period of time.
Particularly, it is an object of the present invention to perform resolution conversion or quantization processing in high quality and high speed.
According to the present invention, the foregoing object is attained by providing an image processing apparatus comprising: expansion means for expanding coded image data; storage means for storing data indicative of characteristics of an image obtained at the time of the expansion processing performed by said expansion means; first conversion means for performing resolution conversion on the image data, expanded by said expansion means, in accordance with the data indicative of the characteristics; and second conversion means for quantizing the image data, on which the resolution conversion is performed, in accordance with the data indicative of the characteristics.
Moreover, according to the present invention, the foregoing object is attained by providing an image processing apparatus comprising: expansion means for expanding coded image data; storage means for storing data indicative of characteristics of an image obtained at the time of the expansion processing performed by said expansion means; and process means for performing quantization processing on the image data expanded by said expansion means, in accordance with the data indicative of the characteristics.
Another object of the present invention is to perform color conversion processing in high quality and high speed.
According to the present invention, the foregoing object is attained by providing an image processing apparatus comprising: expansion means for expanding coded image data; storage means for storing data indicative of characteristics of an image obtained at the time of the expansion processing performed by said expansion means; and process means for performing color conversion processing on the image data expanded by said expansion means, in accordance with the data indicative of the characteristics.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.